Histamine H.sub.1 -receptor antagonists are widely employed in orally for the treatment of bronchial asthma, and it is reported that they often show systemic adverse actions such as sedation or arrhythmogenetic activity. Therefore, topical treatment using the antagonists has been attempted in order to avoid such adverse actions. However, the methods are unsuccessful because the antagonists have strong bronchia irritation when inhaled directly to the bronchia.
Thus, there remains a need for the development of histamine H.sub.1 -receptor antagonists which can be directly inhaled to the bronchia for the treatment of bronchial asthma with less irritation to bronchial tissues.
European Patent Application Unexamined Publication No. 5,318 discloses a benzimidazole compound represented by the formula: ##STR3## wherein Z represents a hydrogen atom or a fluorine atom; A represents a methoxy group, an ethoxy group, a 2-propenyloxy group, a hydroxy group, a methoxycarbonylmethyloxy group, an methoxycarbonylmethyloxy group, a cyanomethyloxy group, a methylthio group, a methanesulfonyl group, an amino group, a nitro group, a fluorine atom or a chlorine atom. In addition, of the above benzimidazole compounds, the compound represented by the formula: ##STR4## has been employed (general name: Astemizole) as oral histamine H.sub.1 -receptor antagonist. However, any topical formulation of this drug applied to the bronchia has not been acceptable in practice due to strong irritation to bronchial tissues.
The 1-(2-benzimidazolyl)-1,5-diazacyclooctane compounds of the present invention are novel compounds, and have not been disclosed or suggested in any prior literature.